Paint spray booths are commonly found in production lines for vehicle bodies and parts. A vehicle body is transported through a paint spray booth where paint is applied to the body and subsequently dried. The paint may be applied by hand, or mechanically by automated equipment. During this painting process some of the paint may not be applied to the vehicle, but rather appears as overspray in the booth atmosphere. This overspray must be removed from the paint spray booth to keep it from falling back on the painted vehicle or from being inhaled by the operators of the equipment.
The paint overspray is typically removed by providing an air flow from a supply plenum above the paint spray booth, through the paint spray booth and out to gas scrubber equipment which removes paint particles from the exhaust gas. It is desirable to maintain the airflow passing over the vehicle being painted turbulance free. This ensures that the air flow does not disturb the uniform paint application to the vehicle. The minimizing of the air flow closely adjacent to the vehicle increases the transfer efficiency of the paint onto the vehicle body. High air flow volumes into that location have a tendency to disrupt the transfer efficiency of the paint being applied onto the vehicle body. Moreover, by reducing the air flow at the central portion the overall volume of the air is reduced. A portion of the air passing through the paint spray booth must be treated with a complicated solvent abatement process, and by reducing the air flow volume, the abatement requirements for cleaning the air are correspondingly reduced. At the same time, it is also desirable to keep the air flow passing over the painting equipment and operators at a higher velocity to prevent the equipment and operators from experiencing paint contamination. However, it is further desirable to minimize air flow in as many non-critical areas as possible in order to decrease energy consumption.
Existing spray booth designs envisage a certain predetermined air flow and flow distribution for the entire spray booth. The plenum has various dampers, diffusers, mixing plates, etc., to provide essentially smooth air flow through the spray zone at a fixed rate of flow. However, in practice, this is rarely achieved due to the non-standard configuration of the booth and the workpiece to be painted, and due to poor air flow design of such spray booths which often causes unwanted turbulence and nonlaminar air flow in critical areas of the spray booth. Poor spray booth air flow causes paint wastage by blowing paint particles in unwanted directions, and often away from the vehicle onto the floor, walls, operator, etc. This is a major cost penalty for manufacturers which are attempting to minimize paint usage and environmental impact.
It is common to have excess air flow in spray booths of up to 20 percent due to poor air supply control. This leads to a significant annual energy penalty for the user. Accordingly, it is desirable to provide a means for accurately and efficiently controlling air speed in various areas of the paint spray booth to optimize flow conditions in certain areas of the booth, and to minimize air flow in those areas in which flow is not required. In current systems, in order to adjust air flow in various areas of the spray booth, individual diffusers must be removed or accessed from above the ceiling for adjustment. This limitation significantly affects energy efficiency and painting performance of a particular spray booth. The performance of the booth is particularly affected by such limitations when the configuration of the article to be painted within the booth is changed, such as a change in car lines, which changes the air flow requirements around the article, which sometimes requires flow adjustment.
It is, therefore, desirable to provide a paint spray booth and air supply arrangement in which multiple air speed zones are provided, and in which air speed may be quickly adjusted without removing diffusers or adjusting them from above the spray booth ceiling.